Celestial News: Dwarf planet update
July 4, 2016
It's been a big year for the dwarf planets in our solar system.
It was about one year ago that the world got its first view of the little planet Pluto, when the New Horizons spacecraft shot through the Pluto system like a speeding bullet.
Due to of the extreme distance of the spacecraft, photographs from the encounter are still trickling back to Earth and will continue to do so for several more months. But, many of Pluto's newly discovered features have already come into sharper focus, as mission scientists pore over the new data as it comes in.
Following is a summary of what we've learned.
Pluto is not the frozen mini-world we expected it to be. First, it turned out to be slightly larger than we thought, enough to confirm that it is, in fact, larger than its cousin, Eris, and still the largest known dwarf planet.
The most prominent feature revealed on Pluto's surface by New Horizons was a bright, heart-shaped region informally named Tombaugh Regio, after Pluto's discoverer. The dearth of impact craters on parts of the heart betrayed its geological youth — less than 10 million years old.
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Scientists now believe the left lobe of the heart, called Sputnik Planum, is a percolating region of frozen nitrogen, carbon monoxide and methane ice. Like a Texas-sized lava lamp, the ice is warmed from below, rises to the surface, cools and flows back down to repeat the cycle.
Surprise. Pluto is still geologically active. Scientists think the energy source driving this activity could be an underground ocean in the process of freezing and releasing heat.
Other features discovered on Pluto include dormant ice volcanoes, frozen nitrogen ponds, mountainous blocks of ice tens of thousands of feet high, vast canyon lands, flowing glaciers and ancient cratered plains.
There is nothing boring about Pluto.
Closer to home, the Dawn spacecraft recently finished its primary mission of mapping the entire surface of dwarf planet Ceres from low orbit. Ceres lies in the asteroid belt between Mars and Jupiter.
Capturing everyone's attention from Dawn's first distant images were the remarkably bright, shiny spots inside of a large crater named Occator. Speculation ran high. Were they ice deposits, salt deposits or something else? The latest data reveal that the bright spots of Occator are most likely deposits of sodium carbonate, or soda ash, a toxic chemical cousin of regular baking soda.
Soda ash can result from the evaporation of mineral-laden water. Fissures caused by the impact that created Occator might have released water from a salty ocean deep under Ceres' crust. This would put Ceres on a very short list of bodies in our solar system with the liquid water necessary to host living organisms.
Finally, the dwarf planet Makemake (pronounced mah-key-mah-key) also made news recently. Located six astronomical units farther out in the solar system than Pluto, Makemake was the only dwarf planet in the outer solar system, until recently, with no known moons.
Pluto has a family of five moons, Eris has one and Haumea has two. Now, astronomers, using the Hubble Space Telescope, have found a moon for Makamake, as well. It is estimated to be about 175 miles in diameter. That leaves Ceres as the only one of the five dwarf planets with no known moons orbiting it — unless you count the Dawn spacecraft as a human-made moon.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Westlake's astrophotography website at jwestlake.com.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Westlake’s astrophotography website at jwestlake.com.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Westlake's astrophotography website at jwestlake.com.